Livestock manure- especially from pigs- has often been thought of as waste. But that’s changing. Many farmers already use it as a fertilizer in their fields. It’s a good alternative to expensive synthetic fertilizers. But could there be a more lucrative uses for pig manure?
A current trend right now that is gaining momentum is converting pig manure to energy. Is it a worthwhile consideration? Read on to learn more.
Manure to Energy
Daniel Andersen is an Iowa State University assistant professor in Agricultural and Biosystems Engineering. He specializes in manure management, and discusses the issue in his blog called, “The Manure Scoop.”
An installment on his blog discusses covered lagoons. Also known as “digester systems,” where liquid and slurry manure are anaerobically digested to create methane gas. In this process, lagoons are covered by a giant plastic sheet. This sheet contains the smelly ammonia gas and liquid, and it keeps rainwater out. Most importantly, it locks in the biogas, or methane that’s naturally produced by the breakdown of the organic matter in the manure. The methane can then be gathered for use.
On the positive side, covered liquid and manure slurry systems could be somewhat smaller, as they would not have to be built to withstand and absorb heavy amounts of rain. Keeping the rainwater out reduces the amount of water that needs to be hauled away in order to utilize it for fertilizer.
It also keeps more nitrogen in the manure, which increases its fertilizer value. Anderson calculates that in typical deep pit storage, 7.8 pounds of ammonia is retained per pig, per year. Changing a system to a covered lagoon would save 5 pounds of ammonia per pig, per year. On a 4,800 hog farm, that would add up to $7000 in nitrogen value each year.
It also helps with odors. And of course, the methane gas produced can be used to generate heat or electricity. Seems genius, right? Why hasn’t the practice taken off?
Not Worth the Effort
Andersen argues that it’s not yet economically viable. The plastic covers alone are a big expense.
Farmers would either need more land on which to spread the extra manure, or would have to move the manure elsewhere, which could potentially increase costs. Theres’s also the added costs of “cleaning the gas to pipeline quality.”
When you put it all together, Anderson has calculated that conversion to this system is pretty much at the breakeven point. For many, that’s just too much “crap” to deal with for little to no cost savings.
Successful Implementation in Australia
According to a recent article on The Pig Site, called Affluent Effluent Possible for Piggeries, 16% of the country’s pig manure is utilized to capture biogas for energy. Australia started their Bioenergy Support Program in 2012. At that time, only 2% of the national herd’s manure was captured for biogas. Since the implementation of the program, the impact has been substantial.
Pig farmers in Australia that have implemented covered manure pits have seen many benefits. Odors are reduced. They save on energy costs by selling excess biogas energy back into the power grid, and they are able to sell carbon credits and renewable energy certificates.
It’s estimated that by 2021, greenhouse gas emissions from Australia’s pork production could drop nearly 30%. The Emissions Reduction fund has issued over $4 million (AUD, $2.8 million USD) worth of carbon credits to participating producers since the beginning of the program. The cutoff for financial feasibility has been found to be around 500 head. But the success thus far has Australia looking into ways to make the practice more practical for smaller operations as well.
Profitable Pig Poo Conclusion
Capturing biogas from manure makes a lot of sense. Odors and greenhouse gas emissions would be reduced. Pig producers could be putting energy back into the power grid. The process of covering manure lagoons reduces the amount of water that gets in, and makes the manure a more potent fertilizer.
But without some kind of financial incentive like they have in Australia, this practice has little likelihood of taking off. To start, a large portion of the country doesn’t even believe the science behind the damaging effects of greenhouse gasses on the environment. Few hog farmers would be willing to cover their lagoons solely because it’s the “right” thing to do. It’s got to be right for their pocketbooks too.
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